GPz305

[SpannerMonkey]

So I've seen these bikes going cheap, and they look nice and retro which suits me... and they're smack bang on the 33bhp limit and spares are plentiful.
I've heard they're brilliant bikes to learn on but I've also heard horror stories about them chewing up camshafts at about 120,000 on the clock or something like that.

What are your guys thoughts on the GPz305?

[warped one]

PM Crazymotorbiker. He had 3 of them one after another.

From what I can remember he didn't have many problems with them, just chewed the belt drive after a while. But plenty of grunt from the parallel twin IIRC and enough to get some speed going with plenty of MPG to save on the pocket.
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amnesia - Never in the history of usernames has one been more accurate. Warped indeed. You sir are a fecking oddball.

[c_dug]

IIRC they are notorious for their badly designed oil pick up which leads to top end damage.

I think Bishbash had one too.
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[stinkwheel]

Lovely bike to ride. Fragile engine which needs to be treated with kidd gloves.

I should know. I've rebuilt three of the fuckers. The first engine suffered a big end failure at 16k miles for no good reason. I rebuilt it, the second threw a conrod through the front of the engine for one of two possible reasons (either me bodging a chipped piston, or the rider ragging the arse off it). Rebuilt it again using parts from another engine, that one had a piston fall apart due to the rider ragging the arse off it and seizing it (which makes me reconsider the cause of the second engine meltdown).

Now most of this was due to a lack of mechanical sympathy on the part of the rider but realistically, they do need to be mollycoddled. It'll do over 100mph and will appear to be quite happy to sit at that for miles and miles... It isn't!

I would personally advise against it. They're cheap for a reason.

Shame really because other than that, they have a hell of a lot going for them, almost the perfect bike for a restricted licence holder. If you could shoehorn a superdream engine into one and retain the belt drive, I reckon you'd have just found nirvana.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[27cows]

I had one and it gave me nothing but trouble. I have rarely been more glad to see the back of a bike. Get a GPz500 instead.
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The RXS100: vehicle of choice for Chuck Norris

[SpannerMonkey]

[andys675]

[27cows]

[SpannerMonkey]

Hmmm, Well bearings are neither here nor there... Easily replaceable.
Ummm, When you say top end issues, what exactly were they? Related to the oil circulation issues I presume?

[stinkwheel]

The only thing a GPZ500 shares with a GPz305 are the first two letters of the model number and the number of cylinders.

Otherwise it is a totally different and superior motorcycle in every way possible.

The GPz305 should be left as a collectors curiosity to be dilligently restored then ridden round a show field a couple of times a year resounding with comments along the lines of "Fucking hell, you remember those? I'm amazed there's still any of them running.".
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Teflon-Mike]

The Z250/305 has always had a marmite fettish, some love them, some loath & I cant offer anythin g that hasn't been said, apart from to think about the 'value'. Theres 'cheap' and there's VFM.
If a very tidy, 305 came along, with few owners, for sensible money, I'd give it a long hard look.
I've heard many critasise them for thier fragile motors, but then I've also known a few that have had them and cranked up a lot of trouble free miles on them..... but they have been middle aged, treated them to new oil at very frequent intervals, looked after them well, and ridden them in very restrained manner to and from work, and on the odd touring holiday.
Those that have had hassle have been younger, bought them becouse they are cheap, and ragged the arse off them trying to keep up with LC's and the like!
So your 'good' one might have a lot of miles on teh clock, but it'll probably have a white rickman top-box and rack on teh back, probably engine protection bars, and if your lucky, heated grips. It'll have an older owner, who'se done all thier own maintenence for the last ten years, and can probably show you every reciept for every oil-change, & he'll be selling it becouse he's 'treated' himself to a Triumph 900 now the mortgage is paid off.... or something like that anyway!
Most, though, will probably be being sold by under 21's who got talked into it by thier Dad, who probably offered the original finance on the thing, becouse it was 'cheap' and it was 'sensible' and was bought of previousely described owner, who worked with the Dad! So, after the first month of getting to grips with a bigger, heavier bike..... it'll have been thrashed mercilessly!
VFM, against a GPz5, well the difference isn't likely to be big money.
If you do 9K miles in a year, your fuel bill alone is likely to be more than you pay for a bike!
GPz5 would probably sell easier in a year or two's time, which may be worth thinking about.
Plenty of tatty & thrashed GPz5's out there too, which possibly pose just as much risk as a 305. Maybe less likely to go wrong, but could prove more expensive to sort if they do.
Quid-per-Q, I dont think theres a lot in it.
A 'good' 305 IF you can tick all the boxs & get some good feelings about the seller, may turn up trumps.
And IF worst comes, possibly cheap enough that you could buy two for the price of one decent GPz5..... but I THINK my inclination, given difference in price between the two, would be to try and find that bit extra for a BETTER example of GPz5
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[stevo as b4]

So are people saying that it's impossible to build a GPZ305 engine that is strong and reliable enough to be ridden hard up to the red zone for hours at a time on a regular basis?

I Know the old 6valve superdream engines both 250 and 400's had thier own top end wear issues (think it was cam and rocker arm wear problems) , but i seem to remember that they were capable of a bit of a thrashing up to around 90mph which was about the max you could get out of them.

[stinkwheel]

[SpannerMonkey]

So basically... Dont touch one with a barge pole? O.o I'm gettin very mixed signals about these bikes. Some are saying they're BRILLIANT... whilst others are saying they're utter shite =(

[27cows]

[stevo as b4]

Cheers stinkwheel, pics show the problem and shortcomings very nicely!

So unless there was a way of getting steel oil pump drive gears made, and a much larger oil pick up fitted, and or uprated oil pump if the capacity is a bit small, then you could never make a 305 engine as strong as a healthy Superdream engine, and capable of the same amount of thrashing?

It is a shame as 36bhp for a 300cc air cooled twin is very good. The superdream 400's were about the same wern't they?

Id be interested to know how robust the early Yamaha and Suzuki 4stroke sporty 250 twins are in comparision to the Honda though, as if i remember the GSX250 was quite a sporty little bike and quick enough for a 4t 250, but i've no idea if the Yam XS250/400 was up to much?

[Kickstart]

Hi

This the big problem with the GPz305 is that basically they are a tuned 250 (and not the strongest 250), hence everything is a bit marginal. Add a badly designed oil system and it is easy to wreck them[/quote]

400 Superdream was a claimed 43hp. However I doubt the accuracy of that (top speed was about 105mph which doesn't need 43hp).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[manuka]

I was the 'unsympathetic' rider who broke her gpz 305 engine three times.

She was called Phoenix, and she was my first bike after passing my test.

It was a nice handling bike and a very comfy saddle. I loved the retro look with the coloured stripes, and I really miss it.

She did break down lots, but very considerately it was always near home.

The honda cb500 I have now is so much more reliable and predictable, but its not the same.

Her memory lives on in a t-shirt that I wear proudly.
"Gpz 305, Air-cooooled"
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"ouch!" said Mr Bump

[.Bishbash.]

Horror stories aside, I had one for a bit, and really enjoyed it. I took Stinkwheels advice and cleaned the oil gauze out, not a bad job to do to be honest and kept the little beauty ticking along. Unti JD got his mitts on it.

The one thing that did pee me off about the bike was the Cam chain tensioner. I was adjusting it every week or two. But if you dont mind doing those jobs then this cheap bike will be up your street.

HTH
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Current bike - GSX-R1000 k8

[wilbur]

[ThoughtContro...]

[27cows]

I actually saw a black GPz305 today. Sitting at the lights beside me, making a bloody horrible top end noise Mind you, the whole bike was a shed. Made my old RXS look almost respectable, and that really takes some doing these days
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The RXS100: vehicle of choice for Chuck Norris

[ThoughtContro...]

Where there never any useful aftermarket mods for the GPz305 back in the day, like a replacement metal oil pump drive sprocket and oil pickup or did no one bother?

Did Kawasaki never bother fixing the design themselves or did they just consign the model to the dustbin of history of poor engine designs?
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Prize cunt
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"In a world of universal deceit telling the truth is a revolutionary act" - George Orwell

[stevo as b4]

I doubt they did, as the GPZ air cooled series was being phased out, and the newer GPZ500 was a very sporty all rounder/commuter with an amazing amount of performance for a 500cc twin at the time! Good ones still get close to 130mph.

Kawasaki also by then had the GPX/ZZR250 about to emerge, and the ZZR250 had 39bhp from a 250cc twin, so that made the old GPZ305 look like it was from the stone age.

[c_dug]